1. Technical Field
The present invention generally relates to fuel control systems for automotive vehicles and, more particularly, to a fuel control system for an automotive vehicle equipped with a dynamic crankshaft fuel control system and an oxygen sensor feedback fuel control system.
2. Discussion
Many modern automotive vehicles are equipped with a dynamic crankshaft fuel control system for controlling engine fueling for a brief period of time after start-up. The dynamic crankshaft fuel control system typically leans the fueling during this period to improve emissions. After the dynamic crankshaft fuel control system has completed its task, fuel control is transferred to an oxygen sensor feedback based fuel control system. Thereafter, fuel delivery is controlled according to the data from the oxygen sensor.
As illustrated in FIGS. 1 and 2, according to the prior art, the transfer of fuel control from the dynamic fuel control system to the oxygen sensor feedback fuel control system, illustrated as dashed line 100, involves a significant change in the amount of fuel delivered to the engine. That is, the prior art transfer of fuel control from lean dynamic crankshaft fuel control to normal oxygen sensor feedback fuel control involves a sudden increase in fuel delivery. This increase in delivered fuel causes an RPM surge and engine racing as shown in FIG. 2.
Advantageously, it has now been found that both dynamic crankshaft fuel control and oxygen sensor feedback fuel control use a proportional-integral-derivative calculation to determine the fuel multiplier which sets the amount of fuel delivered. As such, it would be desirable to use a component of the dynamic crankshaft fuel control proportional-integral-derivative calculation in the initial oxygen sensor feedback fuel control proportional-integral-derivative calculation to smooth the transfer from dynamic crankshaft fuel control to oxygen sensor feedback fuel control.